1. Field of the Invention
The present invention relates to a method and apparatus for non-impact, single-pass printing in which the toner exhibits a selective or "tuned" response to an agent having a preselected characteristic, such as light energy of a particular frequency emitted by a laser, to impart an image to a printing surface or substrate.
The invention may be applied in systems using a single toner or in systems using multiple toners, such as those designed to generate multi-colored output. It is equally applicable to monochrome printing, whether of the single or multiple toner variety, and to color printing. In one particular kind of monochrome printing according to the invention, toners of varying shades, sizes, or both are used to provide an enhanced gray-scale for generating graphics. The invention is well suited for computer printing, color xerography, and facsimile printing, but is not limited to these.
2. Description of the Prior Art
There are a variety of known, non-impact printing techniques that use a laser to produce color images, or more generally, to produce images formed from a plurality of toners, on untreated substrates. These techniques can be classified into one of two main groups depending on whether a single or multiple pass is required to create the final image. None of these techniques, however, utilizes the selective or tuned response invention disclosed herein.
U.S. Pat. No. 3,780,214 (Bestenreiner et al.), for example, describes a method and apparatus for making color prints by using laser energy to sequentially heat certain portions of a plurality of webs, each of which has a single color pigment applied to it, and then transferring each of these images to the paper substrate so that the transferred image from each just-heated web overlies the transferred image from the ones heated earlier. U.S. Pat. No. 4,148,057 (Jesse) discloses a technique of direct laser printing capable of printing on large or irregularly shaped surfaces, as well as of producing three dimensional objects; also disclosed is a means for producing multi-colored images. The techniques disclosed in both these patents, however, require multiple passes to create polychromatic prints. Moreover, there is no suggestion in either patent of utilizing selectivity of the toner to achieve single-pass printing. East German Pat. No. DL 0155507 (Schlegel), in the abstract the present inventor has seen, describes a telex machine in which a thin layer of ink carrier is applied magnetically or electrostatically to paper, then fused to it at particular points by a laser beam. The disclosure pertains to monochrome printing and does not mention any kind of tuned response behavior by a toner.